Sir,

I did something earlier and added a 33 yard zero following Gene's post. Assumptions were as follows:

14.5" barrel
55 gr. Sierra FMJBT
Muzzle velocity 2861 fps
Sight height 3.0 inches

I hope this helps.

ETA: Axis labels got erased, but the vertical axis is inches of drop.

Thank you............... For some reason your last sentence gave me the best laugh of the week, Again Thanks. BTW, I am keeping this short too.

Jatx, if you notice you have three possible zeros, where the bullet crosses the line of sight. Problem with using a close range zero, is that, the zero can be first crossing the line of sight, or the top of the arc of the trajectory.

Hollis, what I understood Gene to be saying was that he was looking for a shorter range zero that would come close to replicating the 300 yard zero, which would be pretty convenient. Maybe I misunderstood him, though.

Please clarify, how is a short range zero problematic so long as you are within max PBR (and you've assumed the right size kill zone)?

I've used this before for a 16" 1:9 m-4gery with decent results. I also have the article LTC Chuck Santos wrote on using a 50yd battlesight zero due to 2" or less deviation at all ranges to 250m. I haven't tried that yet, though, as I don't have a handy 50yd/200m range.

Jatx, Look at your graph. Two references, 1) where the bullet crosses the line up sight on a upward trajectory and then crosses the line of sight on the downward trajectory. 2) where the bullet ceases a upward path and starts to fall (top of arch) at the line of sight. Then note the difference in distance, and keep in mind, the line of sight is a straight line and bullet path is a arc. Also the distance from center of the barrel and center of the sights/scope come into play. The bullet initially needs to rise to meet the line of sight. Sighting in at a longer distance will insure the bullet crosses the line of sight twice. The first crossing is the short distance zero, the second crossing is the long distance zero.

I am not sure if that explains it completely.

H.

This is further complicated on the M-16 series weapons because rather than having sights directly atop the barrel, they are 1.4" above the bore.

TR

A target is nothing more than a physical represenation of a bullet strike at a given range. Personally I use a 1 inch pastie for 99% of my shooting out to ranges of 300 meters.

I also know there's a tgt made specifically for the M4 but as you found out is hard to find. The target I posted is off slightly for the M4 but will work fine for NDD's purpose. (and it free).

Not knowing the ammo type, exact weapon and personnel being trained I figured this target was more than sufficent.

I'm like Gene when it comes to rifle, all I need to know is where I zeroed (at what range) and make adjustments as needed for longer ranges as required.;)

Team Sergeant

Edit to add, if an individual is not keeping a shooting "log" with their rifle then I don't consider them serious shooters anyway.

Sir,

FYI, the free online JBM ballistics calculator allows you to correct for any sight height, which is pretty nice given the variety of mounts, optics and rail systems out there now. It also provides you with PBR and max PBR for any given size kill zone you wish to define.

TR:

I will drop by the committee tomorrow and see if they still have my target. It was clear enough for photographs.

I have also done this on KD ranges using a 300 and 500 elevation with one hold on the target for each elevation.

These are great ways of showing shooters a true trajectory as bullet holes don't lie. What you see on paper is different than what you envision from computer programs.

Gene

Hollis:

I know a cone of fire which is basically the shot group size given a target that is vertical like a KD target. Beaten zone is that cone of fire when it hits the ground which is parallel to the trajectory. You are talking about a point blank zero given a kill zone size and the ordinate of the ammunition being fired.

The hunter still has to estimate range for his bullet to stay within his danger space. He has to be as anal about his range-e as his kill zone is small.

Gene

JTAX:

My 33 yard estimate was about as close as I could get but in no way can I say it is perfect. It is probably within plus or minus three yards of my estimate though.

Try not to make assumptions unless you must. Those computer programs are not perfect by any means. Some emphasize trajectories to about 500 which gives error to ranges past 500. Others emphasize trajectories from 500 to 1000 at the expense of short range precision. Niether will give a perfect representation of what you shoot as ballistic coefficients change with speed. So there are errors involved. These programs will put you on paper at 600 -- generally within plus or minus 1 1/2 minutes. In other words they will give a nine ring elevation. At 1000 one must be on drugs to trust a PC ballistics program to give sufficient accuracy to have confidence a bullet will hit a six foot target frame. The problem is that the shooter doesn't know the time of flight of his particular load to 1000 unless he chronographs it at the barrel and then at 1000 enough times to trust his results.

One thing you should also watch closely is your perception of the path of a trajectory on your PC screen. Your trajectory must be exaggerated in order to show rise and fall on a short screen. It gives the user an illusion of a more parabolic path than the very flattened path found in reality. The computer programs are right, they just have to distort the trajectory to fit on a screen. Unlike the computer programs, shooting on KD ranges to see trajectory gives a very different picture. You will find that the bullet's rising branch is relatively steep for a short distance and then less steep to its ordinate. Past its ordinate it tends to drop relatively uniformly but not perfectly uniform, due to drag. It is really quite interesting to see the differences between reality and the graphics of a computer program.

Gene

Thanks very much for your insights. This is a fascinating topic and I appreciate your words of experience. I'm looking forward to getting back onto a .mil range this summer. :lifter